This disclosure relates generally to wireless communication networks, and more particularly to a method and apparatus for fractional downlink channel coding scheme selection in a general packet radio system.
Wireless communication networks, such as cellular telephone communication networks, are commonplace. Wireless communication networks may comply with one or more standards or recommendations, such as the Global System for Mobile communication (GSM) recommendations. A system operating according to the GSM recommendations will typically include a switching system (SS), a base station system (BSS) and an operation and support system (OSS).
The base station system provides all of the radio-related functions, and the BSS typically includes one or more base station controllers (BSCs) and a plurality of base transceiver stations (BTSs). The base station controller provides all the control functions and physical links between the switching system and the base transceiver station. The base station controller is a high-capacity switch that provides functions such as handover, cell configuration, and control of radio frequency (RF) power levels in the base transceiver stations.
The BTS handles the radio interface to the mobile station (MS). The mobile station is the subscriber equipment used to access the wireless communication network. The base transceiver station includes the radio equipment (transceivers, antennas, amplifiers, etc.) needed to service each cell in the network. A group of base transceiver stations is controlled by a base station controller.
The operation and support system is the functional entity from which the network operator monitors and controls the system. The purpose of the OSS is to provide centralized, regional and localized operation and maintenance activities required for wireless communication network operation. For example, the operation and support system provides a network overview and supports maintenance activities of different operation and maintenance organizations. The operation and support system may include an operation and maintenance center (OMC) coupling all the equipment in the wireless communication network.
The switching system is responsible for performing call processing and subscriber related functions. The switching system includes the home location register (HLR), the mobile services switching center (MSC), visitor location register (VLR), authentication center (AUC) and equipment identity register (EIR).
As the popularity of GSM-based wireless voice communication services increased, so too did the need for nonvoice (i.e., information, data, etc.) wireless communication services. The circuit switched network architecture of GSM, however, proved to be limited in its capability to deliver high speed non-voice communications. As a result, General Packet Radio Service (GPRS) communication networks capable of supplementing circuit switched networks with packet switching functionality have been overlaid on existing wireless communication networks such as GSM.
Using GPRS, non-voice downlink data is separated into related xe2x80x9cpacketsxe2x80x9d by a packet control unit (PCU), the packets with instructions are forwarded to the BTS, the received packets are transmitted as data xe2x80x9cblocksxe2x80x9d by the BTS, and then using the relationship, the MS reassembles the data blocks upon receipt. Thus, the PCU manages, allocates, and schedules the use of packet data resources necessary to establish downlink packet data transmission between the infrastructure and the mobile stations and uplink packet data transmission between mobile stations and the infrastructure. In addition, to reduce the cost of deploying these systems, PCUs may be remotely located from the BTSs that maintain the wireless links between the mobile units and the infrastructure.
Transmission of both downlink and uplink user data is accomplished, via selection and subsequent application by the PCU of one of a number of a GPRS packet data traffic channel (PDTCH) coding schemes. Each of the GPRS PDTCH channel coding schemes offers a different level of error protection at different resource costs; channel coding schemes providing higher error protection requires more resources while channel coding schemes providing lower error protection requires less resources. The selection (based on bit error rates and block error rates of the transmitted user data, local interferers, etc) is based on a number of channel factors and therefore may vary over the life of a data or voice call. Thus, the PCU must dynamically direct the transitions between and among the appropriate GPRS PDTCH coding schemes.
Unfortunately, current methods of transitioning from a lower GPRS PDTCH coding scheme to a higher GPRS PDTCH coding scheme often reflect the consequences of a poor choice by the PCU, and result in high bit error and block error rates, retransmission of data, and overall lower data throughput to an end user.